Formaldehyde-free protein-containing binder compositions

ABSTRACT

A wood-containing composite are described that may include a lignocellulosic material, and a formaldehyde-free binder in contact with at least a portion of the lignocellulose material. The binder is formed from a binder composition that includes a soy flour, a polymer, and a crosslinking agent, at least a portion of each of which are covalently crosslinked to each other in the binder. Also described are methods of making wood-containing composites by providing a pre-mixed, one-part binder composition of at least 60 wt. % soy flour, a polymer, and a crosslinking agent. The binder composition is applied to lignocellulosic material, and the combination may be heated at a temperature of about 100° C. or more to cure the binder composition into a binder. The cured binder has the soy protein, polymer, and crosslinking agent covalently bonded to each other.

This application is a continuation-in-part, and claims the benefit, of co-pending, commonly assigned U.S. patent application Ser. No. 12/697,968, filed Feb. 1, 2010, entitled “Formaldehyde-Free Protein-Containing Binder Compositions,” the entire disclosure of which is herein incorporated by reference for all purposes. Thermoset binders for composite fiber products such as fiberglass insulation and wood composites are moving away from traditional formaldehyde-based compositions. Formaldehyde is considered a human carcinogen, as well as an irritant and allergen, and its use is increasingly restricted in building products, textiles, upholstery, and other materials. In response, binder compositions have been developed that do not use formaldehyde or decompose to generate formaldehyde.

BACKGROUND OF THE INVENTION

One type of these formaldehyde-free binder compositions rely on esterification reactions between carboxylic acid groups in polycarboxy polymers and hydroxyl groups in alcohols. Water is the main byproduct of these covalently crosslinked esters, which makes these binders more environmentally benign, as compared to traditional formaldehyde-based binders. However, these formaldehyde-free binder compositions also make extensive use of non-renewable, petroleum-based ingredients. Thus, there is a need for formaldehyde-free binder compositions that rely less on petroleum-based ingredients.

As an abundant and renewable material, protein has great potential to be an alternative to petroleum-based binders. Proteins are already used extensively as a component of adhesives for various substrates. However, many types of protein-containing adhesives have poor gluing strength and water resistance. Thus, there is a need to improve the bonding strength and water resistance of protein-containing binder compositions to levels that are similar to or better than those of conventional, petroleum-based binder compositions. These and other issues are addressed in the present application.

BRIEF SUMMARY OF THE INVENTION

One-part binder compositions are described that may include one or more proteins that actively crosslink with other binder constituents to provide a rigid thermoset binder. The binder compositions are formaldehyde-free, and incorporate renewable materials like proteins from animal and vegetable sources (e.g., soy flour) that reduce or even eliminate the need for petroleum-based binder ingredients. The components of the binder compositions may be selected to increase the pot life and reusability of pre-cured binder compositions without compromising on the quality of the cured binder product.

The binder compositions may include one-part compositions that can be cured without the addition of another compound. However, additional compounds such as a cure catalyst may optionally be added to accelerate the rate of curing or some other function. In addition, changes in temperature and/or other external conditions may be effected to cure the binder composition and produce a final product containing the cured binder.

Exemplary binder compositions may include at least three components that are all capable of forming covalent bonds with each other. These components may include at least one protein and a combination of two or more crosslinking compounds. The crosslinking compounds may include a first crosslinking compound (e.g., a polymer compound) and a second crosslinking compound (e.g., a crosslinking agent) that are individually crosslinkable with each other and with the protein. For example the binder composition may include a protein, a polymer compound and a crosslinking agent that all have functional groups capable of forming covalent bonds with each other. The protein may include hydroxyl and carboxyl groups that can form covalent bonds with complementary carboxyl and hydroxyl groups on the polymer compound and crosslinking agent. Similarly, the polymer compound and crosslinking agent are selected with complementary functional groups to form covalent bonds with each other (e.g., a polycarboxy polymer and hydroxyl-containing crosslinking agent such as an amino alcohol). When all three components are capable of forming covalent bonds with each other, the crosslinking density in the cured binder may be higher than in binders where only two components form such crosslinking bonds.

The increased crosslinking density in a binder system with three or more covalently bonding compounds may also allow the selection of more stable crosslinking compounds for a one-part binder composition. For example, proteins, polymer compounds, and/or crosslinking agents may be selected that undergo substantially no crosslinking reactions under ambient conditions (e.g., room temperature), thereby extending the pot life (a.k.a. shelf life) of the one-part binder composition. The stability of the individual compounds may be selected to give the one-part binder composition a pot life about 1 month or more.

Embodiments of the invention include one-part thermoset binder compositions that may include a protein and a combination of two or more crosslinking compounds. The crosslinking combination may include a first crosslinking compound and a second crosslinking compound, where the first and second crosslinking compounds are individually crosslinkable with each other and with the protein. One specific, non-limiting example of the present binder compositions includes a polymer compound, such as a polycarboxy polymer; a crosslinking agent crosslinkable with the polymer compound, such as a polyol; and a protein that is crosslinkable with both the polymer compound and the crosslinking agent. The protein may include soy protein which may, for example, be sourced from soy flour.

Embodiments of the invention may further include fiber products. The fiber products may include inorganic or organic fibers (or both) and a cured thermoset binder prepared from a one-part binder composition. The binder composition may include a protein and a combination of two or more crosslinking compounds, where the protein and crosslinking compounds are crosslinkable with each other.

Embodiments of the invention may yet further include wood-containing composites. The composites may be made from a lignocellulose material, and a formaldehyde-free binder in contact with at least a portion of the lignocellulose material. The binder may be formed from a binder composition that includes soy protein, a polymer, and a crosslinking agent, wherein at least a portion of each of which are covalently crosslinked to each other in the cured binder.

Embodiments of the invention may still further include methods of making a fiber product. The methods may include the steps of providing fibers that may be organic fibers or inorganic fibers, and applying a one-part binder composition to the fibers. The one-part binder composition may include a protein and a combination of two or more crosslinking compounds, where the protein and crosslinking compounds are all crosslinkable with each other. The methods may further include reusing an unused portion of the one-part binder solution in a subsequent application of the one-part binder composition to the same fibers or a different group of fibers.

Embodiments of the invention may also include methods of making wood-containing composites. The methods may include providing a pre-mixed, one-part binder composition that includes at least 60 wt. % of a soy protein component (i.e., soy flour), a polymer compound, and a crosslinking agent. The pre-mixed, one-part binder composition may be applied to a lignocellulosic material, and the mixture may be heated at a temperature of about 100° C. or more to convert the binder composition into a binder. The cured binder has the soy protein, polymer, and crosslinking agent covalently bonded to each other in the wood-containing composite.

Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the invention. The features and advantages of the invention may be realized and attained by means of the instrumentalities, combinations, and methods described in the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings wherein like reference numerals are used throughout the several drawings to refer to similar components. In some instances, a sublabel is associated with a reference numeral and follows a hyphen to denote one of multiple similar components. When reference is made to a reference numeral without specification to an existing sublabel, it is intended to refer to all such multiple similar components.

FIG. 1 is a graph of dogbone composite tensile tests for a selection of binder compositions described in the Examples below.

DETAILED DESCRIPTION OF THE INVENTION

One-part binder compositions are described that include renewable materials such as proteins in combination with two or more other binder components. Examples include one-part binder compositions made from at least one protein and a combination of two or more crosslinking compounds, where the protein and crosslinking compounds are all crosslinkable with each other. The term “crosslinkable” refers to the ability of two compounds to form covalent bonds with each other, although other type of bonds may also be formed between the compounds. The one-part binder composition may optionally include additional components such as cure catalysts.

Liquid binder compositions may be applied to substrates such as inorganic and/or organic fibers and cured to make a composite of the thermoset binder and substrate such as a building material (e.g., fiberglass insulation). They may also be applied to lignocellulosic materials such as wood fibers, particles, strips, etc., and formed into a wood-containing composite (e.g., strand board, fiber board, particle board, flake board, wafer board, etc). These materials do not off-gas formaldehyde during their production and use, or decompose to contaminate factories, buildings, homes, and other areas with formaldehyde. Furthermore, the binder compositions may at least partially substitute renewable compounds (e.g., proteins) for non-renewable compounds such as petroleum-based compounds.

Exemplary Binder Compositions:

Exemplary binder compositions may include compositions containing at least one protein and two or more crosslinking compounds, where the protein and crosslinking compounds are crosslinkable with each other. The proteins used in the binder compositions may include vegetable and/or animal proteins. These proteins may be readily available from a renewable source. Examples of proteins that may be used in the binder compositions include soy protein, wheat protein, corn protein, whey, albumin, keratin, gelatin, collagen, gluten, casein, among other kinds of proteins.

The proteins may be used in an unmodified, un-denatured state (i.e., native proteins). Alternatively, the proteins may be modified and/or denatured using physical, chemical, or enzymatic methods that cause changes to the primary, secondary, tertiary, and/or quaternary structures of the proteins. These methods may include denaturing the proteins to change their secondary, tertiary and quaternary structures, and chemically or enzymatically breaking down the protein molecules into smaller fragments. They may also include modifying the pendant moieties of the protein, such as adding additional carboxyl and/or hydroxyl groups to the protein molecules.

One example of a protein used in the invention may be soy protein in the form of a soy flour, soy protein concentrate, soy protein isolate, and/or soy polymer, among other forms of soy protein. Soy flour may be produced by grinding soybeans into a powder. Soy flour may retain the natural oils and other compounds from the soybeans, or may be defatted to produce flour with higher protein content (e.g., about 50 wt % protein or more). Soy protein concentrate contains about 70 wt % soy protein and is made by removing water soluble carbohydrates from defatted soy flour. Soy protein isolate is a highly refined, purified form of soy protein with the protein content of about 90 wt. % or more. The isolates may be made from defatted soy flour that has most non-protein soybean components removed (e.g., fats, carbohydrates, etc.). Soy polymers may include soy proteins that have been chemically modified to impart a variety of functionalities to protein molecules.

The soy protein may be denatured/modified to unfold protein molecules in the dispersion. Upon unfolding, the functionalities of protein molecules (e.g., carboxyl, hydroxyl, and amine) are exposed and may actively react with other binder ingredients to form crosslinking bonds. Examples of protein denaturation and modification methods include, but not limited to, heat treatment, treatment with chaotropic agents (e.g., urea, guanidinium chloride, and lithium perchlorate), acids, bases, metal salts, alcohols, detergents, thiols, sulfites, and mixtures thereof.

The soy protein may also be modified to reduce the viscosity of soy protein dispersion, therefore reducing the viscosity of protein-based thermoset binder compositions. Examples of methods of reducing the viscosity of soy protein dispersion include, but not limited to, hydrolyzing protein using enzymes or alkalis, cleaving disulfide bonds in protein by thiols or sulfites. For example, the viscosity of soy protein dispersion may be reduced by the treatment with sodium bisulfite.

The relative amount of the soy protein component (e.g., soy flour) to add can vary depending on other binder components used, the processing conditions, and the type of end product being made, among other considerations. Embodiments have the concentration of soy protein flour (as a percentage weight of the binder composition) ranging from about 5% to about 95%; about 10% to about 90%; about 25% to about 80%; about 20% to about 60%; about 20% to about 50%; about 30% to about 70%; etc.

Soy protein such as soy flour may be dispersed or dissolved in water. Other binder ingredients, such as the crosslinking compounds (e.g., monomer and polymer compounds, crosslinking agents, etc.), are mixed with the aqueous soy protein dispersion or solution to form the final binder composition that is applied to the fibrous products.

The crosslinking compounds may include monomeric compounds and/or polymer compounds, among other classes of crosslinking compounds. These crosslinking compounds may be selected to have complementary functional groups that can react to form covalent bonds. For example, one crosslinking compound may be a carboxyl-containing polycarboxy polymer, while a second crosslinking compound may be crosslinking agent that includes hydroxyl groups that react to form covalent bonds with the carboxyl groups. Similarly, the polymer compound may have reactive hydroxyl groups and the crosslinking agent may have reactive carboxyl groups that react to form covalent bonds.

Examples of carboxyl-containing polymer compounds include polycarboxy homopolymers and/or copolymers prepared from ethylenically unsaturated carboxylic acids including, but not limited to, acrylic acid, methacrylic acid, butenedioic acid (i.e., maleic acid and/or fumaric acid), methyl maleic acid, itaconic acid, and crotonic acid, among other carboxylic acids. The polycarboxy polymer may also be prepared from ethylenically unsaturated acid anhydrides including, but not limited to, maleic anhydride, acrylic anhydride, methacrylic anhydride, itaconic anhydride, among other acid anhydrides. Additionally, the polycarboxy polymer of the present invention may be a copolymer of one or more of the aforementioned unsaturated carboxylic acids or acid anhydrides and one or more vinyl compounds including, but not limited to, styrenes, acrylates, methacrylates, acrylonitriles, methacrylonitriles, among other compounds. More specific examples of the polycarboxy polymer may include copolymers of styrene and maleic anhydride, and its derivatives including its reaction products with ammonia and/or amines. For example, the polycarboxy polymer may be the polyamic acid formed by the reaction between the copolymer of styrene and maleic anhydride and ammonia.

The polymer compound may be a solution polymer that helps make a rigid thermoset binder when cured. In contrast, when the polymer compound is an emulsion polymer, the final binder compositions are usually less rigid (i.e., more flexible) at room temperature. The polymer compound may include a hydrophobic moiety (e.g., an aromatic ring) that increases the moisture resistance of the cured binder.

Crosslinking agents may include compounds containing at least two reactive functional groups including, but not limited to, hydroxyl, carboxyl, amine, aldehydes, isocyanate, and epoxide, among other functional groups. Examples of crosslinking agents may include polyols, alkanol amines, polycarboxylic acids, polyamines, and other types of compounds with at least two functional groups that can undergo crosslinking of with other binder ingredients, such as proteins and polymer compounds.

Specific examples of polyols may include glycerol, ethylene glycol, propylene glycol, diethylene glycol, and triethylene glycol, among other polyols. Specific examples of alkanol amines may include ethanolamine, diethanolamine, and triethanolamine, among other alkanol amines. Specific examples of polycarboxylic acids may include malonic acid, succinic acid, glutaric acid, citric acid, propane-1,2,3-tricarboxylic acid, butane-1,2,3,4-tetracarboxylic acid, among other polycarboxylic acids. Specific examples of polyamines may include ethylene diamine, hexane diamine, and triethylene diamine, among other polyamines. Specific examples of epoxies may include bisphenol-A based epoxies, aliphatic epoxies, epoxidized oils, among other epoxy compounds.

The crosslinking agent may react with both the polymer compound and the protein. For example, when the polymer compound is a polycarboxy polymer the crosslinking agent may be a polyol that is capable of reacting with not only the protein (e.g., soy protein) but also the polycarboxy polymer.

As noted above, the binder compositions may include three components binders made from a single protein and a two-compound crosslinking combination. In addition, binder compositions may include a plurality of proteins and compounds that make up the crosslinking combination (e.g., a plurality of polymer compounds, and/or crosslinking agents). For example, two or more types of one component may be combined with a single species of each of the other components. In addition, two or more type of two of the components may be combined with a single species of a third component. Also, two or more types of all three components may be present in the binder composition.

The binder compositions may also optionally include a cure catalyst. Examples of cure catalysts may include phosphorous-containing compounds such as phosphorous oxyacids and their salts. For example, the cure catalyst may be an alkali metal hypophosphite salt like sodium hypophosphite (SHP). The cure catalyst may be added to expedite curing of the binder composition.

The binder compositions may also optionally include extenders. Examples of extenders may include starch, lignin, rosin, among other extenders.

The types and concentrations of the binder components help determine the binder composition's pH. Differences in pH can have significant effects on the binder composition, such as the solubility of one or more of the binder components. For example, when the binder composition includes soy protein in an aqueous solution, a pH between about 4 and 5 can cause the protein to start precipitating out of solution. When the pH of the binder composition significantly differs from a target pH, the composition may further include pH adjustment agents that adjust and/or maintain the pH of the binder composition within a desired range. For example, the present binder compositions may include one or more bases that maintain the pH at about 5 or more, about 6 or more, about 7 or more, about 8 or more, about 9 or more, about 9.5 or more, about 10 or more, about 10.5 or more, etc. Specific examples of these bases may include alkali metal hydroxides, and alkali earth metal hydroxides, and ammonium hydroxides among others.

The protein in the binder composition may be actively crosslinkable with the members of the crosslinking combination. The protein may be treated to expose the reactive moieties on polypeptide chains of the proteins (e.g., hydroxyl groups, carboxyl groups, amino groups, thiol groups) for crosslinking reactions. For example, a hydroxyl-containing amino acid moiety on protein chains (e.g., serine, threonine) may react in an esterification reaction with a carboxyl group on the polycarboxy polymer. Similarly, a carboxyl-containing amino acid moiety (e.g., aspartic acid, glutamic acid) may react with a hydroxyl on the crosslinking agent to actively crosslink the protein in the binder composition.

While not wishing to be bound by a particular theory, it is thought that the reactions between reactive moieties on the protein and the crosslinking compounds provide crosslinking among the binder components to create a rigid thermoset binder when cured.

The binder compositions may be pre-mixed, one-part binder compositions having shelf life of about 1 month or more, 6 months or more, etc., without substantial polymerization of the binder components. These highly shelf stable compositions may have protein component concentrations greater than about 40 wt. %, about 50 wt. %, about 60 wt. %, about 70 wt. % about 80 wt. %, about 90 wt. %, about 95 wt. %, etc., where many conventional protein-containing binders containing highly reactive crosslinking compounds begin to cure soon after the components are mixed. In contrast to conventional methods that mix the proteins and other binder components immediately before or during their application to a substrate, the present methods allow the binder composition to be pre-mixed and stored for an extended period prior to use. Among other advantages, this allows the binder solutions to be prepared at one site specialized for making such compositions, and transported to a second site to form the binder-containing composite.

Methods of Making Fiber Products:

The present binder compositions may be used in methods of making fiber products. The methods may include applying a mixture of the binder composition to fibers and curing the binder composition on the fibers to form the fiber product. The binder composition may be spray coated, spin coated, curtain coated, knife coated, or dip coated onto fibers. Once the liquid binder composition is applied, the binder and substrate may be heated to cure the binder composition and form a composite of cured binder and fibers that make up the fiber product.

The binder composition may be formed to have a viscosity in range that permits the efficient application of the solution to the fibers. For example, the viscosity may be about 10 centipoises to about 1000 centipoises when the binder composition is at room temperature (i.e., 20° C.).

If the viscosity of the liquid binder applied to the substrate is too high, it may slow down the application process both at the release point for the binder as well as the rate of mixing and coverage of the binder on the substrate. Solutions and dispersions of many types of protein, including some types of soy protein in aqueous solutions, have generally high viscosities. Thus, the present protein-containing binder compositions may include proteins with a relatively low viscosity when dissolved/dispersed in the liquid binder. These may include soy proteins that are modified to lower the viscosity of soy protein dispersion.

After application of the liquid binder composition on the substrate, the amalgam of liquid binder and substrate undergoes curing. In the curing process the protein, polymer compound, and crosslinking agent may form covalently crosslinked bonds among each other to convert the amalgam into a thermoset composite. When a thermal curing process is used, the amalgam may be subjected to an elevated temperature (e.g., up to 300° C.) to facilitate crosslinking in the binder. The peak curing temperature may depend on the specific formulation of the protein-containing binder composition, the substrate, and whether a cure catalyst is used. The cured material typically includes about 0.5 wt % to about 50 wt % thermoset binder composition (e.g., about 1 wt. % to about 10 wt. %) with the substrate representing most of the remaining weight.

The binder composition may be a stable one-part composition that can be recycled during the application to the fibers and/or between applications on fibers. Thus, an unused portion of the binder composition that, for example, passes through the fibers may be captured and sent back to the supply of binder composition applied to the fibers. In some embodiments, the unused portion of the binder composition may be purified or otherwise treated before returning to the supply.

The reuse of the binder composition may not only reduce the amount of composition used, it may also reduce the amount of waste materials that must be treated and discarded. However, recycling unused binder composition requires that it remain stable for two or more application cycles. In many instances, two-part binder compositions that mix separated and highly reactive components immediately before their application will cure too rapidly to be recycled. One-part binder compositions may also be unsuitable if they don't have a sufficient pot life to remain relatively unreacted prior to reuse and during recycling. The present binder compositions include one-part binder compositions that are stable enough to be appropriate for binder recycling.

Fiber Products:

The present binder compositions may be added to fibers to produce composite fiber products. The fibers may include organic fibers and/or inorganic fibers. For examples of the fibers may include polymer fibers and/or glass fibers, among other types of fibers. The fibers may be arranged as an insulation batt, woven mat, non-woven mat, or spunbond product, among other types of fiber substrate.

The present binder compositions may be used in fiber products to make insulation and fiber-reinforced composites, among other products. The products may include fibers (e.g., organic and/or inorganic fibers) bonded with a cured thermoset binder prepared from a one-part binder composition of a polymer compound, a crosslinking agent that is crosslinkable with the polymer compound, and a protein crosslinkable with both the polymer compound and crosslinking agent. The fibers may include glass fibers, carbon fibers, and organic polymer fibers, among other types of fibers. For example, the combination of the binder composition and glass fibers may be used to make fiberglass insulation products. Alternatively, when the fiberglass is a microglass-based substrate, the binder may be applied and cured to form printed circuit boards, battery separators, filter stock, and reinforcement scrim, among other articles.

Methods of Making Wood-Containing Products:

The present binder compositions may also be used in methods of making wood-containing products (e.g., wood-containing composites). The methods may include applying the binder composition to a lignocellulosic material such as wood chips, wood fibers, wood particles, wood veneer, wood planks, wood blocks, wood wafers, and wood strips, among other lignocellulosic materials. The mixture of the binder composition and the lignocellulosic material may be heated at or above a temperature where the composition starts to crosslink into a cured thermoset binder that bonds together the lignocellulosic material. For example, the temperature of the mixture may be raised to about 100° C. or more to cure the binder composition into a binder that includes a protein (e.g., soy protein), a polymer compound, and a crosslinking agent.

The pre-mixed, one-part binder composition may be applied to the lignocellulosic material by a number of techniques, including spray coating, roller coating, blade coating, disc coating, and bead application, among others. In some instances, the binder solution may be heated or conditioned following its application to increase the tackiness of mixture. This permits the mixture to be more easily shaped and/or molded before curing into the final wood-containing composite.

Following the application of the binder composition and, if performed, the shaping/molding of the combined binder-lignocellulosic mixture, the mixture may be heated to a curing temperature (e.g., about 100° C. or more). Pressure may also be applied during the heating in a hot pressing technique to form the final wood-containing composite. Exemplary hot pressing conditions may include temperatures of about 100° C. to about 250° C. (e.g., about 150° C. to about 200° C.), pressures of about 10 bar to about 100 bar (e.g., about 10 bar to about 40 bar), for a time period of about 10 second or more (e.g., about 30 seconds or more; about 10 seconds to about 300 seconds; etc).

In some examples, the methods may include the formation of a multi-layer composite where at least one of the layers includes a lignocellulosic material. For example, the methods may include forming a mixture of binder composition and lignocellulosic material on a first substrate layer, which may itself contain wood. A second substrate (e.g., another wood-containing layer) may then be applied on top of the mixture to sandwich it between the substrate layers. The substrate layers may then be hot pressed against the mixture to cure the binder composition and form a three-layer composite. The alternate stacking of substrate layers with mixtures of binder composition may be extended to make a multi-layer composite having four, five, six, seven, eight layers, etc.

Wood-Containing Products:

The wood-containing products produced by the present methods may include oriented strand board, medium-density fiberboard, high-density fiberboard, particleboard, flake board, wafer board, parallel-strand lumber, and laminated-strand lumber, among other types of wood-containing products.

EXPERIMENTAL

The following Examples are presented to provide specific representative embodiments. It should be understood, however, that the invention is not limited to the specific details as set forth in these Examples.

Examples #1-8 Preparation & Testing of a Glass-Binder Composite Example #1 Modification of Soy Flour

50 grams of defatted soy flour (Prolia 200/90, Cargill) is dispersed in 200 ml of DI water at room temperature. 0.5 grams of sodium bisulfite is then added to the soy flour dispersion. The viscosity of the soy flour dispersion drops shortly after the addition of the sodium bisulfite. The final soy flour dispersion has a solids concentration of 18.9% by oven method (drying at 125° C. for 2 hours).

Example #2 Modification of Soy Flour

50 grams of defatted soy flour (Prolia 200/90, Cargill) is dispersed in 200 ml of DI water at room temperature. 0.5 grams of sodium bisulfite is then added to the soy flour dispersion. After the viscosity of the soy flour dispersion is decreased to a stable region, the pH of the dispersion is adjusted to 11 using an ammonium hydroxide solution (28-30%). The final soy flour dispersion has a solids concentration of 17.5% by oven method.

Example #3 Preparation of Polyamic Acid Resin (SMAc-TEA)

To a flask equipped with a reflux condenser is added 1,735 grams of water and 234 grams of 28-30% by weight aqueous solution of ammonia. To this solution is added 960 grams of a copolymer of styrene and maleic anhydride (SMA) having a molecular weight of approximately 2,000 and an acid number of 480. The mixture is then heated to 90° C. and maintained at 90° C. under constant stirring until a clear solution of polyamic acid is obtained. To the obtained polyamic acid solution is added 306 grams of triethanolamine. The final polyamic acid resin, hereinafter referred to as SMAc-TEA, has a solids of 42.4% and a pH of 6.8.

Example #4 Preparation of a Binder Composition of Modified Soy Flour and SMAc-TEA

To 79.4 grams of the soy flour dispersion of Example 1 is added with stirring 23.6 grams of the polyamic acid resin of Example 3, and 22 grams of water to achieve a total solids of 20% and a weight ratio between soy flour and SMAc-TEA of 60/40. The final binder composition is then used for dogbone composite tensile test as described below in Example 8.

Example #5 Preparation of a Binder Composition of Modified Soy Flour and SMAc-TEA

To 85.7 grams of the soy flour dispersion of Example 2 is added with stirring 23.6 grams of polyamic acid resin of Example 3 and 15.7 grams of water to achieve a total solids of 20% and a weight ratio between soy flour and SMAc-TEA of 60/40. The final binder composition is then used for dogbone composite tensile test as described below in Example 8.

Example #6 Preparation of a Binder Composition of Modified Soy Flour and SMAc-TEA

To 57.1 grams of the soy flour dispersion of Example 2 is added with stirring 35.4 grams of polyamic acid resin of Example 3 and 32.5 grams of water to achieve a total solids of 20% and a weight ratio between soy flour and SMAc-TEA of 40/60. The final binder composition was then used for dogbone composite tensile test as described below in Example 8.

Example #7 Preparation of a Binder Composition of Modified Soy Flour and SMAc-TEA

To 28.6 grams of the soy flour dispersion of Example 2 is added with stirring 47.2 grams of polyamic acid resin of Example 3 and 49.2 grams of water to achieve a total solids of 20% and a weight ratio between soy flour and SMAc-TEA of 20/80. The final binder composition is then used for dogbone composite tensile test, which is described below in Example 8.

Example #8 Dogbone Composite Tensile Test

The four soy flour-containing binder compositions of Examples 4-7 and SMAc-TEA resin of Example 3 are evaluated via a dogbone tensile test method. Binder solutions are prepared from the five binder compositions by adding 5%, by weight, of sodium hypophosphite monohydrate and 1%, by weight, of aminosilane (Silquest A-1100). The binder solutions are mixed with glass beads to achieve a binder content of 2.4% for each composite of binder and glass beads. The composites are then pressed in molds of dogbone shape to form test samples. The molded samples are then dried and cured in an oven at 204° C. for 20 minutes.

Tensile tests are conducted on the dogbone composite samples before and after humid aging. The aging process involves exposing the dogbone samples containing the cured binder to air at a temperature of 120° F., with 95% relative humidity for 24 hours. FIG. 1 shows the tensile strength results for the five binder compositions described in Examples 3-7 before and after humid aging. In FIG. 1, “SF” stands for “soy flour”. The data shown in FIG. 1 represent the average of nine dogbone specimens for each sample and the error represents the standard deviation.

The tensile tests show that the binder compositions with soy flour that is not ammonia-modified yield a lower tensile strength, as compared to the binder composition without soy flour (e.g., SMAc-TEA). Significant increase in tensile strength was observed when soy flour was ammonia-modified. As shown in FIG. 1, all binder compositions containing ammonia-modified soy flour show higher tensile strength than the binder composition without soy flour (e.g., SMAc-TEA). The humid-aging retention of tensile strength of all the binder compositions containing ammonia-modified soy flour is very high (>95%), indicating the high moisture resistance of the protein-based binder compositions of the present invention.

Examples #9-14 Preparation and Testing of a Wood-Containing Product

The following set of experiments describe the formation and testing of wood-containing products (specifically particleboard) with two formulations of soy protein binder (“A” and “B”). Tests of the thickness swelling, static bending, and internal bond strength of the particleboard samples were performed and compared with a particleboard made from a conventional urea-formaldehyde (UF) binder formulation. The testing revealed that particleboard formed with the soy protein binder formulations had comparable or better water resistance and mechanical properties than the particleboard formed with the UF binder.

Example #9 Preparation of a Soy Flour Dispersion

To a round flask equipped with mechanical stirrer were added 1,540 grams of DI water and 5.5 grams of sodium bisulfite. After the full dissolution of sodium bisulfite, 550 grams of defatted soy flour (Prolia 200/90, Cargill) with the moisture content of 5% were added under constant stirring. The mixture was stirred until a homogenous dispersion was obtained. The resulting soy flour dispersion has a solid content of 25%.

Example #10 Preparation of Crosslinking System

To a round flask equipped with a reflux condenser were added 1,735 grams of water and 302.6 grams of 28-30% by weight aqueous solution of ammonia. To this solution were added 960 grams of a copolymer of styrene and maleic anhydride (SMA) having a molecular weight of approximately 2,000 and an acid number of 480. The mixture was then heated to 90° C. and maintained at 90° C. under constant stirring until a clear solution of polyamic acid is obtained. To the resulting polyamic acid solution were added 306 grams of triethanolamine. The final mixture, hereinafter referred to as SMAc-TEA, has a solid content of 40.2% and a pH of 8.05.

Example #11 Preparation of Soy Protein Binder “A”

To a round flask equipped with mechanical stirrer were added 1,000 grams of the soy flour dispersion of Example 9 and 414.6 grams of SMAc-TEA solution of Example 10 under constant stirring. Separately, 20.8 grams of sodium hypophosphite monohydrate and 10.4 grams of ammonium sulfate were dissolved in 67.4 grams of water; and the solution was then added to the soy flour/SMAc-TEA blend. The resulting binder, hereinafter referred to as Soy Binder A, has the mass ratio between soy flour and SMAc-TEA of 60/40 and a solid content of 29.6%.

Example #12 Preparation of Soy Protein Binder “B”

To a round flask equipped with mechanical stirrer were added 1,000 grams of the soy flour dispersion of Example 9 and 207.3 grams of SMAc-TEA solution of Example 10 under constant stirring. Separately, 10.4 grams of sodium hypophosphite monohydrate and 5.2 grams of ammonium sulfate were dissolved in 25.7 grams of water; and the solution was then added to the soy flour/SMAc-TEA blend. The resulting binder, hereinafter referred to as Soy Binder B, has the mass ratio between soy flour and SMAc-TEA of 75/25 and a solid content of 27.8%.

Example #13 Preparation of Particleboard Samples

Wood chips with the moisture content of 2.40% were used for the core layer of particleboards. Aqueous adhesive binders were mixed with wood chips to achieve 10% binder content for the core layer. Fine wood particles with the moisture content of 2.63% were used for the surface layers of particleboards. Aqueous adhesive binders were mixed with wood particles to achieve 12% binder content for the surface layers.

Particleboards with the surface/core/surface mass ratio of 20/60/20 were prepared by forming surface/core/surface layers sequentially with the respective wood furnish/binder blend in a wooden template. Then the 3-layer assembly was hot pressed to particleboard with the target dimension of 420 mm×220 mm×18 mm. The pressing was conducted in three steps, as shown in Table 1. Depending on the binders, two different press temperatures (190° C. and 210° C.) and two different press times in Step 3 (540 seconds and 660 seconds) were used to make particleboards.

TABLE 1 Pressing Steps for Particleboard Formation Pressure Time Temperarure Step (bar) (sec) (° C.) 1 38 45 190, 210 2 13 15 190, 210 3 38 540, 660 190, 210

Two soy binders, Soy Binder A and Soy Binder B, were used to prepare particleboards. A urea formaldehyde (UF) control binder was also prepared by diluting a commercial UF binder (Prefere 10F106, Dynea) with water to the solids of 30.1% for the surface layers and 34.0% for the core layer.

Example 14 Testing of the Particleboard Samples

Particleboard samples were tested to measure the following characteristics:

1. Thickness Swelling and Water Sorption

Swelling tests were conducted based on EN 317 standard. Three 50 mm×50 mm samples cut from each particleboard were placed vertically in a temperature controlled water pool at 20° C. for 24 hours. Thickness was measured in the center of each sample. Thickness swelling was calculated using the following equation: Thickness swelling [%]=(T ₂ −T ₁)/T ₁*100, where T₁ is the initial thickness and T₂ is the thickness after 24-hour immersion.

Water absorption was calculated using the following equation: Water absorption [%]=(m ₂ −m ₁)/m ₁*100, where m₁ is the initial mass, and m₂ is the mass after 24-hour immersion. 2. Static Bending (MOE/MOR)

Static bending tests were conducted based on EN 310 standard with some deviations. Deviations from the standard are the length of the panels (400 mm) and the diameter of the cylindrical punch (10 mm). Two 400 mm×50 mm board samples from each particleboard were tested using Universalprüfmaschine Frank 81565.

3. Internal Bond Strength (IB)

Internal bond strength tests were conducted based on EN319 standard. Three 50 mm×50 mm samples from each particleboard were tested using Universalprüfmaschine Zwick Z010.

The results of the tests on the particleboard samples are summarized below in Table 2:

TABLE 2 Pre-press Total 24-hr Internal Moisture Press Board 24-hr Water Thickness Bond Content (%) Time Density Absorption Swelling MOE MOR Strength Binder Surface Core (sec) [g/cc] (%) (%) (MPa) (MPa) (MPa) UF* 23.0 17.8 600 0.69 75.2 26.9 2700 7.9 0.06 Soy Binder A** 23.5 20.6 720 0.74 72.3 31.4 3272 14.8 0.19 Soy Binder A** 23.5 20.6 600 0.71 78.7 36.8 2730 10.5 0.19 Soy Binder B** 25.2 22.0 720 0.74 69.4 25.0 3430 16.7 0.40 *Press temperature: 190° C. **Press temperature: 210° C.

Compared with the UF control, particleboards made with the soy binders exhibit good swelling and mechanical properties. The modulus of elasticity (MOE), modulus of rupture (MOR), and internal bond strength of the particleboards containing soy binder are higher than the control boards with UF binder.

Having described several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present invention. Accordingly, the above description should not be taken as limiting the scope of the invention.

Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges may independently be included or excluded in the range, and each range where either, neither or both limits are included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a process” includes a plurality of such processes and reference to “the protein” includes reference to one or more proteins and equivalents thereof known to those skilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and “includes” when used in this specification and in the following claims are intended to specify the presence of stated features, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, integers, components, steps, acts, or groups. 

What is claimed is:
 1. A wood-containing composite comprising: a lignocellulosic material; and a formaldehyde-free binder in contact with at least a portion of the lignocellulose material, wherein the formaldehyde-free binder is formed from an aqueous mixture comprising soy flour dispersed in an aqueous solution of a solution polymer of styrene and maleic anhydride, and a crosslinking agent, wherein the aqueous solution does not include an emulsion of the solution polymer or the crosslinking agent, and wherein at least a portion of each of the soy flour, the solution polymer, and the crosslinking agent are covalently bonded to each other in the binder.
 2. The wood-containing composite of claim 1, wherein the crosslinking agent comprises an amino alcohol.
 3. The wood-containing composite of claim 2, wherein the crosslinking agent comprises triethanolamine.
 4. The wood-containing composite of claim 1, wherein the lignocellulose material comprises one or more materials selected from the group consisting of wood chips, wood fibers, wood particles, wood veneer, wood planks, wood blocks, wood wafers, and wood strips.
 5. The wood-containing composite of claim 1, wherein the composite comprises oriented strand board, medium density fiberboard, high density fiberboard, particleboard, flake board, wafer board, parallel-strand lumber, or laminated-strand lumber.
 6. The wood-containing composite of claim 1, wherein the formaldehyde-free binder comprises at least 60 wt. % of the soy flour.
 7. The wood-containing composite of claim 1, wherein the formaldehyde-free binder comprises at least 90 wt. % of the soy flour.
 8. A method of making a wood-containing composite, the method comprising: providing one-part binder composition comprising an aqueous mixture of: at least 60 wt. % soy flour; and an aqueous solution of: a solution polymer of styrene and maleic anhydride; and a crosslinking agent, wherein the aqueous solution does not include an emulsion of the solution polymer or the crosslinking agent; applying the formaldehyde-free one-part binder composition to a lignocellulosic material; and heating the mixture of the binder composition and the lignocellulosic material at a temperature of about 100° C. or more to cure the binder composition into a binder, wherein the binder has at least a portion of the soy protein, the solution polymer, and the crosslinking agent covalently bonded to each other.
 9. The method of claim 8, wherein the one-part binder composition has a pH of about 5 or more.
 10. The method of claim 8, wherein the one-part binder composition has a viscosity of about 1 to about 1000 centipoises at 20° C.
 11. The method of claim 8, wherein the heating of the mixture of the binder composition and the lignocellulosic material comprises hot pressing the mixture at the temperature of about 100° C. or more for a time period of 30 seconds or more.
 12. The method of claim 11, wherein the hot pressing step comprises: applying the mixture of the binder solution and the lignocellusloic material on a first substrate layer; applying a second substrate layer on the mixture and the first substrate layer to form a multi-layer assembly; and pressing the multi-layer assembly at the temperature of about 100° C. or more for a time period of 30 seconds or more to form the wood-containing composite.
 13. The method of claim 12, wherein the first and second substrate layers are surface layers comprising wood.
 14. The method of claim 8, wherein the one-part binder composition comprises about 60 wt. % to about 95 wt. % soy flour.
 15. The method of claim 8, wherein the crosslinking agent comprises triethanolamine.
 16. A formaldehyde-free, one-part binder composition comprising an aqueous mixture of: about 60 wt. % to about 95 wt. % soy flour; and an aqueous solution of: a solution polymer of styrene and maleic anhydride; and a crosslinking agent, wherein the aqueous solution does not include an emulsion of the solution polymer or the crosslinking agent; wherein at least a portion of the solution polymer, the crosslinking agent and soy protein from the soy flour covalently crosslink to each other when the binder composition is cured at a temperature of about 100° C. or more, and wherein the binder composition has a pH of about 5 or more, and a shelf-life of about 1 month or more.
 17. The binder composition of claim 16, wherein the crosslinking agent comprises a hydroxyl-containing crosslinking agent.
 18. The binder composition of claim 16, wherein the crosslinking agent comprises triethanolamine.
 19. The binder composition of claim 16, wherein the composition has a pH of about 6 to about
 9. 20. The binder composition of claim 16, wherein the binder composition has a viscosity of about 1 to about 1000 centipoises at 20° C. 